Morbid Obesity Increases Cost and Complication Rates in Spinal Arthrodesis

Study Design. A retrospective cross-sectional study of all spinal fusions in California from 2003 to 2007. Objective. This study analyzes whether morbid obesity alters rates of complications and charges in patients undergoing spinal fusion. Summary of Background Data. Prior studies of obesity have focused on lumbar fusion; some identified increases in wound complications. However, these studies typically do not account for comorbidities, do not examine nonlumbar fusions, and usually are small single institution series. Methods. Our study used the Healthcare Cost and Utilization Project's California State Inpatient Databases (CA-SID) to identify normal weight and morbidly obese patients admitted in California between 2003 and 2007 for 4 types of spinal fusion: anterior cervical fusion (International Classification of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM] procedure code 810.2), posterior cervical fusion (810.3), anterior lumbar fusion (810.6), and posterior lumbar fusion (810.8). Demographic, comorbidity, and complications data were collected. Primary outcome was in-hospital complication; secondary outcomes were total cost, length of stay, and in-hospital mortality. Multivariate logistic regression was performed. Results. In total 84,607 admissions were identified, of which 1455 were morbidly obese. Morbid obesity was associated with 97% higher in-hospital complication rates (13.6% vs. 6.9%), sustained across nearly all complication types (cardiac, renal, pulmonary, wound complications, among others). Mortality among the morbidly obese was slightly higher (0.41 vs. 0.13, P < 0.01) as were average hospital costs ($108,604 vs. $84,861, P < 0.0001). Length of stay was longer as well (4.8 d vs. 3.5 d, P < 0.0001). All effects were less pronounced in posterior cervical fusions. On multivariate analysis, morbid obesity was the most significant predictor of complications in the anterior cervical and posterior lumbar fusion groups (more than age, demography, and other comorbidity). Conclusion. Morbid obesity seems to increase the risk of multiple complication types in spinal fusion surgery, most particularly in anterior cervical and posterior lumbar approaches.